Hide absence-reason-chip in ManageStudentsDialog.vue if the person is not absent

aleksis/apps/alsijil/frontend/components/coursebook/absences/ManageStudentsDialog.vue

@@ -152,6 +152,7 @@ export default {
             v-if="item.absenceReason || item.notesWithExtraMark?.length > 0"
           >
             <absence-reason-chip
+              v-if="item.absenceReason"
               small
               :absence-reason="item.absenceReason"
               class="mr-1"